Mendelian trait/disorder: yes

Mode of inheritance: Autosomal Recessive Lethal

Considered a defect: yes

Key variant known: yes

Year key variant first reported: 2018

Species-specific symbol: HH6

History: Fritz et al. (2018) "adopted the nomenclature HH6 . . . to acknowledge the previous discoveries and molecular characterizations of the HH1 [OMIA 000001-9913], HH3 [OMIA 001824-9913], HH4 [OMIA 001826-9913], and HH5 [OMIA 001941-9913] embryonic lethal mutations. The HH6 haplotype and HH6 mutation studied in this article should not be confused with the haplotype provisionally named HH6 in Fritz et al. (2013), which was actually associated with the mutation causing complex vertebral malformation" [OMIA 001340-9913].

Mapping: Using the homozygous haplotype deficiency strategy, Fritz et al. (2018) mapped an autosomal recessive embryonic lethal trait to a 1.1Mb region on chromosome BTA16.

Molecular basis: Within the mapped candidate region (see Mapping section), Fritz et al. (2018) identified a likely causal variant as "an A-to-G transition at position 29,773,628 bp on chromosome 16 (g.29773628A>G; rs434666183)". The authors explained that "This A-to-G transition changes the initiator ATG (methionine) codon to ACG because the gene is transcribed on the reverse strand. . . . Initiation of translation at the closest in-frame Met codon would truncate SDE2 by 83 amino acids, including an 8-amino acid motif conserved among eukaryotes".

Breed: Holstein.

Associated gene: